The present invention relates to integrated circuits (I.C.s) suitable for use as image array sensors, and in particular, for use as multi-spectral image array sensors.
I.C. image array sensors are commonly used in solid state cameras and colour image sensors are known which comprise a two-dimensional array of sensing cells which is provided with a matrixed pattern of colour filters, for example, red, green and blue filters. The array has a plurality of rows and columns of sensing cells and outputs from the sensing cells are read out individually, row by row, at a single array output the output of neighbouring cells being read sequentially. Horizontal and vertical shift registers are normally used for this purpose. Cell outputs corresponding to different colours are demultiplexed at the array output and fed to respective colour channels.
Commonly, neighbouring sensing cells in the array have different colour filters in order to achieve appropriate spatial sampling of radiation of each colour being sensed for each colour channel of the sensor. Since the outputs of neighbouring cells are read out sequentially, the cell outputs form a signal stream at the array output of inherently fluctuating form due to the different colour radiation sensed by neighbouring cells xe2x80x94even in image areas which have a constant colour across a number of neighbouring cells, where that colour corresponds to different signal levels on the different colour channels. This fluctuating signal results in one or more relatively high frequency signal components at the array output whose amplitude is related to background chromaticity as well as to image scene luminance.
Such high frequency signal component(s) lead to interference between neighbouring sensing cell output signals and consequently to corruption of the image chromaticity interpreted by circuits which follow the sensor, producing visual image error effects in a camera in which the sensor is used. Moreover, if the sensing cell matrixed colour filter pattern is not the same in all respects for each row of the array, then the resulting chromaticity errors also differ from row to row, producing more visually offensive image errors.
Additionally, the fluctuating signal stream at the array output including the associated spurious high frequency signal components, can be difficult to handle in the analogue domain in which such image array sensors normally operate.
It is an aim of the present invention to overcome or reduce one or more of the foregoing disadvantages.
According to a first aspect of the invention we provide an integrated circuit suitable for use as a multi-spectral image array sensor in a solid state camera system having a plurality of channels for radiation of different wavelengths, the integrated circuit comprising an array of sensing cells having at least one row of sensing cells, each sensing cell being formed and arranged for sensing radiation corresponding to one of said channels, said at least one row containing a plurality of series of sensing cells which series are interspersed with each other in a predetermined manner, each series consisting essentially of sensing cells for a respective one of said plurality of channels, and readout means for reading signal outputs from the cells in said at least one cell row of the array, wherein said readout means is adapted to read consecutively, in use of the integrated circuit, the signal outputs from the sensing cells in each one of said plurality of series of cells in said at least one row.
One advantage of the integrated circuit according to the invention is that the sensing cell outputs for the cells of at least two series, preferably each series, of cells in said at least one row, can be read out consecutively at the array output. Thus, the cell outputs from sensing cells for the same channel of said plurality of channels can be read out consecutively. This minimises fluctuation in the array output signal stream due to variations in individual cell output signals from cells formed and arranged for sensing radiation of different wavelengths since the difference in radiation and hence signal level between successive cells for the same channel are often much smaller than the difference in radiation and hence signal level between neighbouring cells for different channels.
The readout means may comprise an address decode system which is configured to read consecutively the outputs from the sensing cells in each one of said plurality of series of cells in said at least one row of the array.
Alternatively, and preferably, the readout means comprises horizontal scanning means coupled to each cell in the array for scanning said at least one cell row of the array, wherein the horizontal scanning means comprises at least two horizontal shift register means, each horizontal shift register means being coupled to the cells of a respective one of said plurality of interspersed series of cells.
The array of sensing cells may be a one-dimensional array having a single row of sensing cells. Such an array may, for example, be suitable for use in an image scanning device.
Preferably, the array is a two-dimensional array having a plurality of rows and columns of sensing cells with a vertical scanning means also coupled to each cell in the array. Each row of cells of the two-dimensional array may contain a plurality of series of sensing cells which series are interspersed with each other in a predetermined manner, each series consisting essentially of sensing cells for a respective one of said plurality of channels. Preferably, each row contains the same number of interspersed series of sensing cells. Preferably, the plurality of series of cells contained in each row are interspersed in the same predetermined manner. The number of horizontal shift register means provided is also preferably equal to the number of said interspersed series of cells in each row. Thus, the sensing cell outputs for each series of cells in each row can be read out consecutively.
Each horizontal shift register means preferably comprises at least one horizontal shift register. Thus it would be possible to have more than one horizontal shift register for a given series of cells.
Adjacent sensing cells in each row may be formed and arranged for sensing radiation of wavelengths corresponding to different ones of said plurality of channels. The integrated circuit may be suitable for use as a colour image sensor wherein said plurality of channels are for radiation corresponding to respective different colours. For example, there may be three colour channels corresponding respectively to red, green and blue radiation wavelengths. Each row may, for example, contain three series of sensing cells, for sensing red, green and blue wavelength radiation respectively. The three series of cells may be interspersed such that each row contains an alternating pattern of red (R), green (G), and blue (b), sensing cells e.g. R G B R G B R G . . . Alternatively, each row may, for example, contain only two series of sensing cells. The two series of cells in each row may be arranged so that every third cell senses a different colour radiation to every first and second cell e.g. B B R B B R B B R . . . Said interspersed series of sensing cells contained in any one row may comprise sensing cells for sensing at least one different colour radiation to the sensing cells of the interspersed series of cells in another row. For example, a first row may contain two series of cells for sensing red and blue radiation and a second row may contain two series of cells for sensing red and green radiation. Where each row contains two interspersed series of cells, the array of cells may be arranged in a Bayer matrix pattern in which the two series of cells in each odd-numbered row are interspersed to form an alternating pattern of cells for sensing a first colour and a second colour, e.g. G R G R G R . . . , and the two series of cells in each even-numbered row are interspersed to form an alternating pattern of cells for sensing the first colour and a third colour, e.g. B G B G B G . . . With this arrangement, there are preferably provided two horizontal shift registers for reading the outputs from the sensing cells of respective ones of the two interspersed series of cells in every row of the array.
The or each horizontal shift register of each said horizontal shift register means preferably comprises a plurality of shift register elements each of which elements is coupled to a respective one of the sensing cells in each row of the array. The shift register elements of said at least two horizontal shift register means may conveniently be interleaved to provide a compact arrangement of the horizontal shift registers in the integrated circuit layout. For example, where the sensing cells of the array are arranged in a Bayer matrix pattern and two horizontal shift registers are provided, the shift register elements may be interleaved in an alternating pattern.
The integrated circuit is preferably fabricated using MOS or CMOS technology.
The integrated circuit may additionally be capable of sensing radiation at non-visible wavelengths, for example, infra-red radiation. Thus, for example, at least one of said plurality of channels may be for infra-red or other non-visible radiation and some of the sensing cells may consequently be for sensing infra-red or other non-visible radiation respectively.
The array of sensing cells may include a matrixed pattern of filters corresponding to different radiation wavelengths so as to enable essentially similar sensing cells to sense radiation at a particular wavelength, or over a particular band of wavelengths, corresponding to a respective one of said plurality of channels. Alternatively there could be cells having sensing surfaces responsive to different radiation wavelengths.
According to a second aspect of the invention we provide a method of reading the outputs of individual sensing cells of an array of sensing cells fabricated in an integrated circuit suitable for use as a multi-spectral image array sensor in a solid camera system having a plurality of channels for radiation of different wavelengths, the array comprising at least one row of sensing cells, said at least one row containing a plurality of series of sensing cells which series are interspersed with each other in a predetermined manner and each series consisting essentially of sensing cells for a respective one of said plurality of channels, wherein the method comprises reading consecutively the sensing cell output signals from the cells in each one of said plurality of series of cells in said at least one row.
The method preferably uses a separate horizontal shift register means to read the cell outputs for the cells of respective ones of the plurality of interspersed series of cells in said at least one row.
Where the array of sensing cells is a two-dimensional array having a plurality of rows and columns, each row containing a plurality of series of sensing cells which series are interspersed with each other in a predetermined manner, each series consisting essentially of sensing cells for a respective one of said plurality of channels, the method comprises reading consecutively the sensing cell output signals from the cells in each one of said plurality of series of cells in each row.
Preferably, the sensing cell outputs signals from the cells in each one of said plurality of series of cells in said at least one row are read consecutively into signal processing means which are adapted to demultiplex said sensing cell output signals into respective ones of said plurality of channels for radiation of different wavelengths.
According to a third aspect of the invention we provide a solid state camera head incorporating at least one lens and an integrated circuit as aforedescribed.
According to a fourth aspect of the invention we provide a solid state camera system having a plurality of channels for radiation of different wavelengths and incorporating an integrated circuit as aforedescribed.
According to a fifth aspect of the invention we provide signal processing means suitable for use in a solid state camera system and adapted to receive and demultiplex streams of output signals from sensing cells of an image sensing array of the camera system, said array having at least one row of sensing cells containing a plurality of series of sensing cells interspersed in a predetermined manner, each series consisting essentially of sensing cells for a respective one of a plurality of channels for radiation of different wavelengths in the solid state camera system, said signal processing means being adapted to demultiplex a shuffled stream of output signals from sensing cells in said at least one row into respective ones of said plurality of channels, in which shuffled stream of output signals the output signals from the sensing cells in each one of said plurality of series of cells in said at least one row are arranged consecutively.
Preferably, the signal processing means is adapted to receive streams of output signals from each row of a two-dimensional image sensing array of the solid state camera system, each row comprising a plurality of series of sensing cells interspersed with each other in a predetermined manner and each series consisting essentially of sensing cells for a respective one of said plurality of channels, said signal processing means being adapted to demultiplex a shuffled stream of sensing cell output signals from each row into respective ones of said plurality of channels, wherein in each said shuffled stream of output signals the output signals from the sensing cells in each one of said plurality of series of cells in the respective row are arranged consecutively.
According to a sixth aspect of the invention we provide a data recording medium having recorded thereon image data comprising at least one shuffled sensing cell output signal stream from an image sensing array having at least one row of sensing cells, said at least one row comprising a plurality of series of sensing cells interspersed with each other in a predetermined manner and each series consisting essentially of sensing cells for sensing a predetermined range of wavelengths of electromagnetic radiation, in which said at least one shuffled sensing cell output signal stream the output signals from the sensing cells in each one of said plurality of series of cells are arranged consecutively.